The present invention relates to a unit and a method for duplex call control for SVC (Switched Virtual Channel) connection, which is implemented as an ATM switch, an ATM subscriber line concentrator, etc. having duplex composition composed of an operating (working) system and a standby (protection) system.
In ATM (Asynchronous Transfer Mode) networks, three protocols are used as control protocols for establishing/releasing SVC (Switched Virtual Channel) connection. The first is a protocol according to ITU-T Q.2110 (hereafter, referred to as xe2x80x9cSSCOP (Service Specific Connection Oriented Protocol)xe2x80x9d). The second is a protocol according to ITU-T Q.2130 (hereafter, referred to as xe2x80x9cSSCF (Service Specific Coordination Function)xe2x80x9d). The third is a protocol for the signaling layer, according to ITU-T Q.2931, ITU-T Q.2971, ATM Forum Technical Committee UNI (User-Network Interface) Specification Version 3.1 (hereafter, referred to as xe2x80x9cUNI3.1xe2x80x9d), or ATM Forum Technical Committee ATM UNI Signaling Specification Version 4.0 (hereafter, referred to as xe2x80x9cUNI4.0xe2x80x9d). Each of the four standard specifications (ITU-T Q.2931, ITU-T Q.2971, UNI3.1, UNI4.0) for the signaling layer is hereafter referred to as xe2x80x9cUNI signalingxe2x80x9d.
FIG. 1 is a block diagram showing an example of the composition of a conventional duplex call control unit. The conventional duplex call control unit shown in FIG. 1 is composed of an operating (working) system (including an ATM switch section 100a and a call control section 101a), a standby (protection) system (including an ATM switch section 100b and a call control section 101b), and line interface sections 102a, 102b, . . . , 102n. The operating system ATM switch section 100a and the standby system ATM switch section 100b are connected to the line interface sections 102a, 102b, . . . , 102n via buses 151a, 151b, 150, 154a, 154b, . . . , 154n. The standby system ATM switch section 100b can not receive ATM cells from the line interface sections 102a, 102b, . . . , 102n via the buses 151b, 150, 154a, 154b, . . . , 154n until a switch-over from the operating system ATM switch section 100a occurs. The operating system ATM switch section 100a is connected to the operating system call control section 101a via a bus 152a, and the standby system ATM switch section 100b is connected to the standby system call control section 101b via a bus 152b. The operating system call control section 101a and the standby system call control section 101b are connected together via a bus 153. The line interface sections 102a, 102b, . . . , 102n transmit and receive ATM cells to/from ATM networks or subscriber terminals via ATM lines 155a, 155b, . . . , 155n, respectively.
The operating system ATM switch section 100a receives ATM cells via the bus 151a, extracts call control cells for SVC connection (VPI=0, VCI=5) from the ATM cells, and sends the extracted call control cells to the operating system call control section 101a via the bus 152a. The operating system call control section 101a which received the call control cells executes call control according to the call control cells. In the call control, the operating system call control section 101a communicates UNI signaling messages of the signaling layer by use of the call control cells. The operating system call control section 101a first receives a UNI signaling message xe2x80x9cSETUPxe2x80x9d and transmits the UNI signaling message xe2x80x9cSETUPxe2x80x9d to the destination of the SVC connection. When a UNI signaling message xe2x80x9cCONNECTxe2x80x9d from the destination arrived, the operating system call control section 101a sets SVC connection information (as the result of the call control) to the operating system ATM switch section 100a, and thereby establishes the SVC connection. The operating system call control section 101a sends the SVC connection information of the established SVC connection only, to the standby system call control section 101b via the bus 153. The standby system call control section 101b which received the SVC connection information sets the same SVC connection information to the standby system ATM switch section 100b and thereby establishes the same SVC connection (as the SVC connection which has been set to the operating system ATM switch section 100a) to the standby system ATM switch section 100b. When failure or maintenance occurred to the operating system ATM switch section 100a or the operating system call control section 101a, the bus 151a for connecting the operating system ATM switch section 100a and the bus 150 is disabled and the bus 151b for connecting the standby system ATM switch section 100b and the bus 150 is enabled, thereby the reception and transmission of ATM cells are thereafter executed by the standby system ATM switch section 100b. Thereafter, the standby system call control section 101b executes the call control.
However, in the conventional duplex call control unit which has been explained above, SSCOP link connections are necessitated to be disconnected when the switch-over from the operating system to the standby system is executed. Information concerning the SSCOP layer which is being operated is not communicated between the operating system call control section 101a and the standby system call control section 101b, therefore, mismatch of the SSCOP layer status occurs between the operating system call control section 101a and the standby system call control section 101b. Therefore, the SSCOP layer status of the standby system call control section 101b on the switch-over becomes different from peer protocol, that is, mismatch of the SSCOP layer status occurs between the standby system call control section 101b and an adjacent ATM switch or a subscriber terminal which has been linked with the operating system call control section 101a, and thus the SSCOP link connections are necessitated to be disconnected on the switch-over.
Due to the disconnection of the SSCOP link connections, some of signaling messages which should be communicated via the SSCOP link connections are missed or lost, and thereby a call during establishment/release of the SVC connection is necessitated to be interrupted.
It is therefore the primary object of the present invention to provide a duplex call control unit and a duplex call control method for SVC connection by which the disconnection of the SSCOP link connections on the switch-over from the operating system to the standby system is eliminated, information concerning established SVC connection can be held on the switch-over, and call control for a call during SVC connection establishment/release can also be continued and executed normally on the switch-over.
In accordance with a first aspect of the present invention, there is provided a duplex call control unit comprising a first ATM switch section, a second ATM switch section, a first call control section, a second call control section, a call control parameter database section, a control section, a first switch-over section and a second switch-over section. The first ATM switch section for switching ATM cells extracts call control cells for establishment/release of SVC connection from ATM cells which are supplied via ATM lines, and when call control cells as response are supplied thereto, inserts the call control cells in proper ATM cells and outputs the ATM cells including the call control cells so as to be transmitted to proper ATM lines. The second ATM switch section also executes the above operations of the ATM switch section similarly to the first ATM switch section. The first call control section receives call control cells which has been extracted by the first ATM switch section or the second ATM switch section, outputs call control cells as response to the first ATM switch section or the second ATM switch section, and when call control for an SVC connection is completed, sets SVC connection information to the first ATM switch section or the second ATM switch section. The second call control section also executes the above operations of the call control section similarly to the first call control section. The call control parameter database section stores call control parameters with respect to SVC connection information with regard to SVC connection which has already been established and call control parameters with respect to the statuses of call control protocols for SVC connection which is being established or being released. The call control parameters stored in the call control parameter database section are referred to by the first call control section or the second call control section that is operating as a standby system call control section or that is restarting working, for adjusting its call control parameters. The control section monitors operating statuses of the first ATM switch section, the second ATM switch section, the first call control section and the second call control section, and outputs instructions concerning bus connection depending on the monitored operating statuses. The first switch-over section switches bus connection between the ATM lines and the ATM switch sections according to the instructions supplied from the control section so that the aforementioned operations of the ATM switch section can be executed at least by the first ATM switch section or the second ATM switch section that is working. The second switch-over section switches bus connection between the ATM switch sections and the call control sections according to the instructions supplied from the control section so that the aforementioned operations of the call control section can be executed at least by the first call control section or the second call control section that is working.
In accordance with a second aspect of the present invention, in the first aspect, the call control parameters with respect to SVC connection information include xe2x80x9cVPI (Virtual Path Identifier)xe2x80x9d, xe2x80x9cVCI (Virtual Channel Identifier)xe2x80x9d, xe2x80x9ctraffic informationxe2x80x9d, xe2x80x9cband widthxe2x80x9d, and xe2x80x9ccall referencexe2x80x9d.
In accordance with a third aspect of the present invention, in the second aspect, the call control parameter xe2x80x9ctraffic informationxe2x80x9d includes xe2x80x9cpriorityxe2x80x9d and xe2x80x9cQoS (Quality of Service)xe2x80x9d.
In accordance with a fourth aspect of the present invention, in the first aspect, the call control parameters with respect to call control protocol statuses include call control parameters for the SSCOP layer, SSCF layer and call control parameters for the signaling layer.
In accordance with a fifth aspect of the present invention, in the fourth aspect, the call control parameters for the SSCOP layer include xe2x80x9cSSCOP state variablesxe2x80x9d, xe2x80x9cSSCOP timer valuexe2x80x9d, xe2x80x9cSSCOP parametersxe2x80x9d, xe2x80x9cmaximum SSCOP SDU sizexe2x80x9d, and xe2x80x9cmaximum SSCOP UU size(j)xe2x80x9d for each SSCOP link connections.
In accordance with a sixth aspect of the present invention, in the fourth aspect, the call control parameters for the SSCF layer include xe2x80x9cSSCF state variablesxe2x80x9d for each SSCOP link connections.
In accordance with a seventh aspect of the present invention, in the fourth aspect, the call control parameters for the signaling layer include xe2x80x9ccall referencexe2x80x9d and xe2x80x9cstatus for call referencexe2x80x9d for each calls.
In accordance with an eighth aspect of the present invention, in the first aspect, in the case where the control section detected that all of the four monitored components are working, the control section instructs the first switch-over section to execute bus connection for transferring the ATM cells supplied via the ATM lines to both the first ATM switch section and the second ATM switch section and transmitting ATM cells supplied from the first ATM switch section to the ATM lines, and instructs the second switch-over section to execute bus connection for transferring the call control cells extracted by the first ATM switch section to both the first call control section and the second call control section, transferring the call control cells as response outputted by the first call control section to the first ATM switch section, transferring SVC connection information outputted by the first call control section as the result of the call control to the first ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section. In the case where the control section detected that the first call control section out of the four monitored components is not working, the control section instructs the first switch-over section to execute bus connection for transferring the ATM cells supplied via the ATM lines to both the first ATM switch section and the second ATM switch section and transmitting ATM cells supplied from the first ATM switch section to the ATM lines, and instructs the second switch-over section to execute bus connection for transferring the call control cells extracted by the first ATM switch section to the second call control section, transferring the call control cells as response outputted by the second call control section to the first ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to both the first ATM switch section and the second ATM switch section. In the case where the control section detected that the first ATM switch section out of the four monitored components is not working, the control section instructs the first switch-over section to execute bus connection for transferring the ATM cells supplied via the ATM lines to the second ATM switch section and transmitting ATM cells supplied from the second ATM switch section to the ATM lines, and instructs the second switch-over section to execute bus connection for transferring the call control cells extracted by the second ATM switch section to both the first call control section and the second call control section, transferring the call control cells as response outputted by the second call control section to the second ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section. In the case where the control section detected that the first call control section and the first ATM switch section out of the four monitored components are not working, the control section instructs the first switch-over section to execute bus connection for transferring the ATM cells supplied via the ATM lines to the second ATM switch section and transmitting ATM cells supplied from the second ATM switch section to the ATM lines, and instructs the second switch-over section to execute bus connection for transferring the call control cells extracted by the second ATM switch section to the second call control section, transferring the call control cells as response outputted by the second call control section to the second ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section.
In accordance with a ninth aspect of the present invention, there is provided a duplex call control method for controlling a duplex call control unit which is provided with a first ATM switch section, a second ATM switch section, a first call control section and a second call control section. The first ATM switch section for switching ATM cells extracts call control cells for establishment/release of SVC connection from ATM cells which are supplied via ATM lines, and when call control cells as response are supplied thereto, inserts the call control cells in proper ATM cells and outputs the ATM cells including the call control cells so as to be transmitted to proper ATM lines. The second ATM switch section also executes the above operations of the ATM switch section similarly to the first ATM switch section. The first call control section receives call control cells which has been extracted by the first ATM switch section or the second ATM switch section, outputs call control cells as response to the first ATM switch section or the second ATM switch section, and when call control for an SVC connection is completed, sets SVC connection information to the first ATM switch section or the second ATM switch section. The second call control section also executes the above operations of the call control section similarly to the first call control section. The duplex call control method comprises a call control parameter storage step, a call control parameter reference step and a bus connection control step. In the call control parameter storage step, call control parameters with respect to SVC connection information with regard to SVC connection which has already been established and call control parameters with respect to the statuses of call control protocols for SVC connection which is being established or being released are stored in a call control parameter database section to be referred to by the first call control section or the second call control section for adjusting its call control parameters. In the call control parameter reference step, the call control parameters stored in the call control parameter database section is referred to by the first call control section or the second call control section that is operating as a standby system call control section or that is restarting working, and thereby call control parameters of the call control section is adjusted. In the bus connection control step, operating statuses of the first ATM switch section, the second ATM switch section, the first call control section and the second call control section are monitored, and instructions concerning bus connection are generated and outputted depending on the monitored operating statuses so as to control bus connection of a first switch-over section which is provided between the ATM lines and the ATM switch sections and bus connection of a second switch-over section which is provided between the ATM switch sections and the call control sections so that the aforementioned operations of the ATM switch section can be executed at least by the first ATM switch section or the second ATM switch section that is working and so that the aforementioned operations of the call control section can be executed at least by the first call control section or the second call control section that is working.
In accordance with a tenth aspect of the present invention, in the ninth aspect, the call control parameters with respect to SVC connection information include xe2x80x9cVPI (Virtual Path Identifier)xe2x80x9d, xe2x80x9cVCI (Virtual Channel Identifier)xe2x80x9d, xe2x80x9ctraffic informationxe2x80x9d, xe2x80x9cband widthxe2x80x9d, and xe2x80x9ccall referencexe2x80x9d.
In accordance with an eleventh aspect of the present invention, in the tenth aspect, the call control parameter xe2x80x9ctraffic informationxe2x80x9d includes xe2x80x9cpriorityxe2x80x9d and xe2x80x9cQoS (Quality of Service)xe2x80x9d.
In accordance with an twelfth aspect of the present invention, in the ninth aspect, the call control parameters with respect to call control protocol statuses include call control parameters for the SSCOP layer, SSCF layer and call control parameters for the signaling layer.
In accordance with a thirteenth aspect of the present invention, in the twelfth aspect, the call control parameters for the SSCOP layer include xe2x80x9cSSCOP state variablesxe2x80x9d, xe2x80x9cSSCOP timer valuexe2x80x9d, xe2x80x9cSSCOP parametersxe2x80x9d, xe2x80x9cmaximum SSCOP SDU sizexe2x80x9d, and xe2x80x9cmaximum SSCOP UU size(j)xe2x80x9d for each SSCOP link connections.
In accordance with a fourteenth aspect of the present invention, in the twelfth aspect, the call control parameters for the SSCF layer include xe2x80x9cSSCF state variablesxe2x80x9d for each SSCOP link connections.
In accordance with a fifteenth aspect of the present invention, in the twelfth aspect, the call control parameters for the signaling layer include xe2x80x9ccall referencexe2x80x9d and xe2x80x9cstatus for call referencexe2x80x9d for each calls.
In accordance with a sixteenth aspect of the present invention, in the bus connection control step of the ninth aspect, in the case where all of the four monitored components are detected to be working, the first switch-over section is instructed to execute bus connection for transferring the ATM cells supplied via the ATM lines to both the first ATM switch section and the second ATM switch section and transmitting ATM cells supplied from the first ATM switch section to the ATM lines, and the second switch-over section is instructed to execute bus connection for transferring the call control cells extracted by the first ATM switch section to both the first call control section and the second call control section, transferring the call control cells as response outputted by the first call control section to the first ATM switch section, transferring SVC connection information outputted by the first call control section as the result of the call control to the first ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section. In the case where the first call control section out of the four monitored components is detected to be not working, the first switch-over section is instructed to execute bus connection for transferring the ATM cells supplied via the ATM lines to both the first ATM switch section and the second ATM switch section and transmitting ATM cells supplied from the first ATM switch section to the ATM lines, and the second switch-over section is instructed to execute bus connection for transferring the call control cells extracted by the first ATM switch section to the second call control section, transferring the call control cells as response outputted by the second call control section to the first ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to both the first ATM switch section and the second ATM switch section. In the case where the first ATM switch section out of the four monitored components is detected to be not working, the first switch-over section is instructed to execute bus connection for transferring the ATM cells supplied via the ATM lines to the second ATM switch section and transmitting ATM cells supplied from the second ATM switch section to the ATM lines, and the second switch-over section is instructed to execute bus connection for transferring the call control cells extracted by the second ATM switch section to both the first call control section and the second call control section, transferring the call control cells as response outputted by the second call control section to the second ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section. In the case where the first call control section and the first ATM switch section out of the four monitored components are detected to be not working, the first switch-over section is instructed to execute bus connection for transferring the ATM cells supplied via the ATM lines to the second ATM switch section and transmitting ATM cells supplied from the second ATM switch section to the ATM lines, and the second switch-over section is instructed to execute bus connection for transferring the call control cells extracted by the second ATM switch section to the second call control section, transferring the call control cells as response outputted by the second call control section to the second ATM switch section, and transferring SVC connection information outputted by the second call control section as the result of the call control to the second ATM switch section.
In accordance with seventeenth through twenty-second aspects of the present invention, there are provided machine-readable record mediums storing programs for instructing a microprocessor unit etc. to execute duplex call control processes according to the duplex call control methods of the eighth, ninth, eleventh, twelfth, thirteenth and fourteenth aspects of the present invention.